Author: Cornelis, K.
Paper Title Page
MOPIK045 SPS Slow Extraction Losses and Activation: Challenges and Possibilities for Improvement 611
 
  • M.A. Fraser, B. Balhan, H. Bartosik, C. Bertone, D. Björkman, J.C.C.M. Borburgh, N. Conan, K. Cornelis, R. Garcia Alia, L. Gatignon, B. Goddard, Y. Kadi, V. Kain, A. Mereghetti, F. Roncarolo, P.M. Schicho, J. Spanggaard, O. Stein, L.S. Stoel, F.M. Velotti, H. Vincke
    CERN, Geneva, Switzerland
 
  In 2015 the highest integrated number of protons in the history of the North Area was slow extracted from the CERN Super Proton Synchrotron (SPS) for the Fixed Target physics programme. At well over 1.1019 protons on target (POT), this represented the highest annual figure at SPS for almost two decades, since the West Area Neutrino Facility was operational some 20 years ago. The high intensity POT requests have continued into 2016-17 and look set to do so for the foreseeable future, especially in view of the proposed SPS Beam Dump Facility and experiments, e.g. SHiP*, which are requesting up to 4·1019 POT per year. Without significant improvements, the attainable annual POT will be limited to well below the total the SPS machine could deliver, due to activation of accelerator equipment and associated personnel dose limitations. In this contribution, the issues arising from the recent high activation levels are discussed along with the steps taken to understand, manage and mitigate these issues. The research avenues being actively pursued to improve the slow extraction related beam loss for present operation and future requests are outlined, and their relative merits discussed.
*A. Golutvin et al., ‘‘A Facility to Search for Hidden Particles (SHiP) at the CERN SPS'', CERN, Geneva, Switzerland, Rep. CERN-SPSC-2015-016 (SPSC-P-350), Apr. 2015.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK045  
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MOPIK046 Phase Space Folding Studies for Beam Loss Reduction During Resonant Slow Extraction at the CERN SPS 615
 
  • L.S. Stoel, M. Benedikt, K. Cornelis, M.A. Fraser, B. Goddard, V. Kain, F.M. Velotti
    CERN, Geneva, Switzerland
 
  The requested number of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) for Fixed Target (FT) physics is expected to continue increasing in the coming years, especially if the proposed SPS Beam Dump Facility is realised. Limits on the extracted intensity are already being considered to mitigate the dose to personnel during interventions required to maintain the extraction equipment, especially the electrostatic extraction septum. In addition to other on-going studies and technical developments, a reduction of the beam loss per extracted proton will play a crucial role in the future performance reach of the FT experimental programme at the SPS. In this paper a concept is investigated to reduce the fraction of beam impacting the extraction septum by folding the arm of the phase space separatrix. Beam dynamics simulations for the concept are presented and compared to the phase space acceptance of the extraction channel. The performance potential of the concept at SPS is evaluated and discussed alongside the necessary changes to the non-linear optical elements in the machine.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK046  
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MOPIK049 SPS Slow Extracted Spill Quality During the 2016 Run 627
 
  • V. Kain, J. Bauche, P. Catherine, K. Cornelis, M.A. Fraser, L. Gatignon, C.M. Genton, B. Goddard, K. Kahle, M. Magrans de Abril, O. Michels, L.S. Stoel, F.M. Velotti
    CERN, Geneva, Switzerland
 
  The flux of particles slow extracted with the 1/3 integer resonance from the Super Proton Synchrotron at CERN should ideally be constant over the length of the extraction plateau, for optimum use of the beam by the fixed target experiments. The extracted intensity is controlled in feed-forward correction of the horizontal tune via the main SPS quadrupoles. The Mains power supply noise at 50 Hz and harmonics is also corrected in feed-forward by small amplitude tune modulation at the respective frequencies with a dedicated additional quadrupole circuit. In 2016 the spill quality could be much improved with respect to the situation of the previous year with more performant algorithms. In this paper the improved tools are described and the characteristics of the SPS slow extracted spill in terms of macro structure and typical frequency content are shown. Other sources of perturbation were, however, also present in 2016 which frequently caused the spill quality to be much reduced. The different effects are discussed and possible or actual solutions detailed. Finally, the evolution of the spill quality during characteristic periods in the 2016 run is presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK049  
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TUPIK086 Modelling the Radioactivity Induced by Slow-Extraction Losses in the CERN SPS 1897
 
  • M.A. Fraser, D. Björkman, K. Cornelis, B. Goddard, V. Kain, P.M. Schicho, C. Theis, H. Vincke
    CERN, Geneva, Switzerland
 
  Resonant slow extraction is used to provide an intense quasi-DC flux of high-energy protons for the Fixed Target (FT) physics programme at the CERN Super Proton Synchrotron (SPS). The unavoidable beam loss intrinsic to the extraction process activates the extraction region and its equipment. Although the radiation dose to equipment has an impact on availability, the cool-down times required to limit dose to the personnel carrying-out maintenance of the accelerator also pose important restrictions, and ultimately limit the number of protons on target. In order to understand how the extracted proton flux affects the build-up and subsequent cool-down of the induced activation, a model based on a simple empirical relationship has been developed and shown to predict the measured radioactive decay at ionisation chambers located along the extraction region. In this contribution, the empirical model is described, its strengths and limitations discussed, and its application as a predictive tool for estimating cool-down times as a function of extracted proton flux demonstrated.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK086  
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TUPVA128 Performance of the CERN Injector Complex and Transmission Studies into the LHC during the Second Proton-Lead Run 2395
 
  • R. Alemany-Fernández, S.C.P. Albright, M.E. Angoletta, J. Axensalva, W. Bartmann, H. Bartosik, P. Baudrenghien, G. Bellodi, A. Blas, T. Bohl, E. Carlier, S. Cettour-Cave, K. Cornelis, H. Damerau, A. Findlay, S.S. Gilardoni, S. Hancock, A. Huschauer, M.A. Jebramcik, S. Jensen, J.M. Jowett, V. Kain, D. Küchler, A.M. Lombardi, D. Manglunki, T. Mertens, M. O'Neil, S. Pasinelli, Á. Saá Hernández, M. Schaumann, R. Scrivens, R. Steerenberg, H. Timko, V. Toivanen, G. Tranquille, F.M. Velotti, F.J.C. Wenander, J. Wenninger
    CERN, Geneva, Switzerland
 
  The LHC performance during the proton-lead run in 2016 fully relied on a permanent monitoring and systematic improvement of the beam quality in all the injectors. The beam production and characteristics are explained in this paper, together with the improvements realized during the run from the source up to the flat top of the LHC. Transmission studies from one accelerator to the next as well as beam quality evolution studies during the cycle at each accelerator, have been carried out and are summarized in this paper. In 2016, the LHC had to deliver the beams to the experiments at two different energies, 4 Z TeV and 6.5 Z TeV. The properties of the beams at these two energies are also presented  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA128  
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WEPVA110 Analysis and Operational Feedback on the New Design of the High Energy Beam Dump in the CERN SPS 3524
 
  • P. Rios Rodriguez, J.A. Briz Monago, M. Calviani, K. Cornelis, S. De Man, R. Esposito, S.S. Gilardoni, B. Goddard, J.L. Grenard, D. Grenier, M. Grieco, J. Humbert, V. Kain, F.M. Leaux, C. Pasquino, A. Perillo-Marcone, J.R.F. Poujol, S. Sgobba, D. Steyart, F.M. Velotti, V. Vlachoudis
    CERN, Geneva, Switzerland
 
  CERN's Super Proton Synchrotron (SPS) high-energy internal dump (Target Internal Dump Vertical Graphite, known as TIDVG) is required to intercept beams from 102 to 450 GeV. The equipment installed in 2014 (TIDVG#3) featured an absorbing core composed of different materials surrounded by a water-cooled copper jacket, which hold the UHV of the machine. An inspection of a previous equipment (TIDVG#2) in 2013 revealed significant beam induced damage to the aluminium section of the dump, which required imposing operational limitations to minimise the risk of reproducing this phenomenon. Additionally, in 2016 a vacuum leak was detected in the dump assembly, which imposed further limitations, i.e. a reduction of the beam intensity that could be dumped per SPS supercycle. This paper presents a new design (TIDVG#4), which focuses on improving the operational robustness of the device. Moreover, thanks to the added instrumentation, a careful analysis of its performance (both experimentally and during operation) will be possible. These studies will help validating technical solutions for the design of the future SPS dump to be installed during CERN's Long Shutdown 2 in 2020 (TIDVG#5).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA110  
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THPAB146 Investigation of the Remanent Field of the SPS Main Dipoles and Possible Solutions for Machine Operation 4069
 
  • F.M. Velotti, H. Bartosik, J. Bauche, M.C.L. Buzio, K. Cornelis, M.A. Fraser, V. Kain
    CERN, Geneva, Switzerland
 
  The CERN Super Proton Synchrotron (SPS) provides different types of beams at different extraction energies. The main magnets of the SPS are regulated with a current loop, but it has turned out that hysteresis effects from the main dipoles have a significant impact on reproducibility and hence efficiency and availability. Beam and machine parameters were found to depend on the programmed sequence of magnetic cycles - the so-called super cycle - representing the production of the different beams. The scientific program of the SPS requires frequent changes of the supercycle composition and the effect of the main magnet hysteresis has to be understood, modelled and used in accelerator control system. This paper summarises the first main field measurements carried out with the currently available systems during operational conditions as well as measurements of vital machine and beam parameters as a function of the super cycle composition. Finally, ideas will be presented to provide reproducibility by automatically correcting different parameters taking the magnetic history of the main magnets into account.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB146  
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THPAB147 Automatic Local Aperture Measurements in the SPS 4073
 
  • V. Kain, H. Bartosik, S. Cettour Cave, K. Cornelis, F.M. Velotti
    CERN, Geneva, Switzerland
 
  The CERN SPS (Super Proton Synchrotron) serves as LHC injector and provides beam for the North Area fixed target experiments. It is equipped with flat vacuum chambers to accommodate the large horizontal beam size required during transition crossing and slow extraction. At low energy, the vertical acceptance becomes critical with high intensity large emittance fixed target beams. Optimizing the vertical available aperture is a key ingredient to optimize transmission and reduce activation around the ring. Aperture measurements are routinely carried out after each shutdown. Global vertical aperture measurements are followed by detailed bump scans at the locations with the loss peaks. During the 2016 run a tool was developed to provide an automated local aperture scan around the entire ring. This allowed to establish detailed reference measurements of the vertical aperture and identify directly the SPS aperture bottlenecks. The methodology applied for the scans will be briefly described in this paper and the analysis discussed. Finally, the 2016 SPS measured vertical aperture will be presented and compared to the results obtained with the previous method.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB147  
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